Magnetoencephalography (MEG) has long held the promise of providing a non-invasive tool for localizing epileptic seizures in humans due to its high spatial resolution compared to the scalp electroencephalogram (EEG). Yet, this promise has been elusive, not due to a lack of sensitivity or spatial resolution, but due to the fact that he large size and immobility of present cryogenic (superconducting) technology prevents long-term telemetry often required to capture these very infrequent epileptiform events. To circumvent this limitation, this project will be devoted to the development of a practical non-cryogenic (room temperature) microfabricated atomic magnetometer (magnetrode) based on laser spectroscopy of rubidium vapor and similar in size and flexibility to scalp EEG electrodes. The project is based on our published preliminary results in which we used Micro-Electro-Mechanical Systems (MEMS) technology to construct a working miniature magnetrode and tested it in an animal model to measure neuronal currents of single epileptic discharges and more subtle spontaneous brain activity with a high signal-to-noise ratio approaching that of present superconducting sensors. These measurements are a promising step toward the goal of high- resolution noninvasive telemetry of epileptic events in humans with seizure disorders, and form the foundation of the present proposal. The immediate objectives of this project will be to solve key issues involved in bridging the gap between our present prototype magnetrode and one that can be practically applied for presurgical evaluation of epilepsy patients. These issues center on reducing noise and increasing sensitivity to eventually permit scalp measurements of ictal onset and interictal spikes in both superficial and deep temporal lobe regions. To this end, we will develop our magnetrode into a gradiometer to reduce noise, transform our new methods for actively canceling magnetic field gradients near a stationary recording locus into a novel tracking coil system to cancel gradients in moving (recumbent but not restrained) patients and construct a prototype multi-channel magnetrode for field mapping and active noise cancellation (AIM 1), optimize source modeling and implement software shielding with the multi-channel magnetrode (AIM 2), and perform proof of concept measurements of auditory evoked fields and seizures using magnetrode telemetry in epilepsy patients (AIM 3). If successful, the results of this project will provide both the technological basis and justification for our longer-range goal f developing a high-resolution multichannel MEG system for mobile telemetry of human epilepsy in an unshielded or minimally shielded environment, as well as telemetry of other neurological disorders (and the normal behaving brain) where extended mobile neuroimaging is essential.